A re-evaluation of marine nematode productivity

Abstract

Nematodes are the most abundant multicellular animals in marine sediments but their role in the benthos has not been properly quantified yet. In nearly all energy-flow budgets of marine systems their annual production P is given as about nine times their mean biomass B and their part in the total energy-flow is consequently estimated as anywhere between 3 and 30% of the total (carbon) input in the benthic system. Our laboratory experiments demonstrate that nematode productivity is much higher than P/B ∼ 9 per year and may reach values of over 60 for bacterial grazers. To obtain more reliable estimates for field populations we propose a regression equation relating egg-to-egg development time Tmin to temperature (t) and adult female weight (W in µg wet weight):log Tmin = 2.202−0.0461 t + 0.627 log W. When multiplied by the constant biomass turnover per generation (P/B)gen = 3, development rate 1/Tmin is a good predictor of daily P/B. This method was applied to two series of field data. A rather stable community from a sublittoral mud in the North Sea had an annual P/B = 20. A less stable Aufwuchs community from Sargassum in Japan had an annual P/B = 58.